/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.nineoldandroids.animation;

/**
 * This evaluator can be used to perform type interpolation between
 * <code>int</code> values.
 */
public class IntEvaluator implements TypeEvaluator<Integer> {

	/**
	 * This function returns the result of linearly interpolating the start and
	 * end values, with <code>fraction</code> representing the proportion
	 * between the start and end values. The calculation is a simple parametric
	 * calculation: <code>result = x0 + t * (v1 - v0)</code>, where
	 * <code>x0</code> is <code>startValue</code>, <code>x1</code> is
	 * <code>endValue</code>, and <code>t</code> is <code>fraction</code>.
	 *
	 * @param fraction
	 *            The fraction from the starting to the ending values
	 * @param startValue
	 *            The start value; should be of type <code>int</code> or
	 *            <code>Integer</code>
	 * @param endValue
	 *            The end value; should be of type <code>int</code> or
	 *            <code>Integer</code>
	 * @return A linear interpolation between the start and end values, given
	 *         the <code>fraction</code> parameter.
	 */
	public Integer evaluate(float fraction, Integer startValue, Integer endValue) {
		int startInt = startValue;
		return (int) (startInt + fraction * (endValue - startInt));
	}
}